The very limited information concerning the physiological capacities and adaptive potential of females to heat strain and work suggested the need to interrelate the levels of certain specific circulating hormones to the physiological responses and adaptative qualities of women subjected to this combination of stresses. It is proposed to make cross-sectional studies of the influence of/on these hormonal balances in women under a variety of combinations of heat strain, work loads, exercise duration, and levels of physical fitness. Acclimatization of females to work in the heat, as well as at rest, will be studied and comparisons made to relate to various phases of the mentrual cycle, prepubertal, and menopausal states, etc. These studies will consider temperature regulation, circulatory adjustments, capacity of sweat glands to produce sweat, and the electrolyte composition of the sweat. These studies are designed to increase our understanding of the differences between men and women in terms of their functional capacities and adaptative potentials.